The Simulation Hypothesis DRONEFACE

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But the branch of the that readers might find most interesting led to humans. Humans are in the phylum, and the last common ancestor that founded the Chordata phylum is still a mystery and understandably a source of controversy. Was our ancestor a ? A ? Peter Ward made the case, as have others for a long time, that it was the sea squirt, also called a tunicate, which in its larval stage resembles a fish. The nerve cord in most bilaterally symmetric animals runs below the belly, not above it, and a sea squirt that never grew up may have been our direct ancestor. Adult tunicates are also highly adapted to extracting oxygen from water, even too much so, with only about 10% of today’s available oxygen extracted in tunicate respiration. It may mean that tunicates adapted to low oxygen conditions early on. Ward’s respiration hypothesis, which makes the case that adapting to low oxygen conditions was an evolutionary spur for animals, will repeatedly reappear in this essay, as will . Ward’s hypothesis may be proven wrong or will not have the key influence that he attributes to it, but it also has plenty going for it. The idea that fluctuating oxygen levels impacted animal evolution has been gaining support in recent years, particularly in light of recent reconstructions of oxygen levels in the eon of complex life, called and , which have yielded broadly similar results, but their variances mean that much more work needs to be performed before on the can be done, if it ever can be. Ward’s basic hypotheses is that when oxygen levels are high, ecosystems are diverse and life is an easy proposition; when oxygen levels are low, animals adapted to high oxygen levels go extinct and the survivors are adapted to low oxygen with body plan changes, and their adaptations helped them dominate after the extinctions. The has a pretty wide range of potential error, particularly in the early years, and it also tracked atmospheric carbon dioxide levels. The challenges to the validity of a model based on data with such a wide range of error are understandable. But some broad trends are unmistakable, as it is with other models, some of which are generally declining carbon dioxide levels, some huge oxygen spikes, and the generally relationship between oxygen and carbon dioxide levels, which a geochemist would expect. The high carbon dioxide level during the Cambrian, of at least 4,000 PPM (the "RCO2" in the below graphic is a ratio of the calculated CO2 levels to today's levels), is what scientists think made the times so hot. (Permission: Peter Ward, June 2014)

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After as little as a half-million years of bedraggled survivors adapting to ice age seas, the ice sheets retreated and the oceans rose. The of the time may have also changed, and upwelling, anoxia, and other dramatic chemistry and nutrient changes happened. Those dynamics are suspected to be responsible for the second wave of extinctions. There also seem to have been .Atmospheric oxygen levels may have fallen from around 20% to 15% during the Ordovician, which would have contributed to the mass death. Seafloor anoxia seems to have been particularly lethal to continental-shelf biomes, possibly all the way to shore. It took the ecosystems millions of years to recover from the Ordovician-Silurian mass extinction, but basic ecosystem functioning was not significantly altered in the aftermath, which is why a has been proposed as a more significant extinction event. The were laid down by the . Most oil deposits were formed in the era of dinosaurs and the processes of oil deposit formation were similar; they were related to oceanic currents. When currents came to shore via the bottom and the prevailing winds blew the top waters offshore, it became a and anoxic sediments could form. When the winds blew onshore and left via the bottom, the waters became clear and are known as nutrient deserts. The oscillation between nutrient traps and nutrient deserts can be seen in oil deposit sediments. In the mid-20th century, Soviet scientists revived an old hypothesis that oil was , a variation of which was also championed by , but improving tools and investigation invalidated those hypotheses. No petroleum geologists today seriously consider the abiogenic origin of hydrocarbons. Oil sediment formation events seem related to mantle and crust processes that created high sea levels and anoxic events, and the last great one was in the , which formed more than 10% of the world's oil deposits.

Except for New Guinean highlanders, initial European contact with all of those relict populations was universally disastrous, just as and elsewhere for centuries. Those initial contacts happened in anthropology’s early days, and studied the Andamans in the early 20th century, when they were tattered remnants of the people of a century earlier. The people were also devastated by European invasion. When the Dutch invaded what became South Africa, the Southern San were driven to extinction while the !Kung survived in the . Andamans, !Kung, and Aboriginal Australians all had/have strikingly similar religious ceremonies, which were marathon singing and dancing sessions that could last all night. Some rituals lasted for months. Their rituals are very likely what the first religions looked like, which were strenuous ordeals in which people reached frenzied states that left them exhausted. Today’s leading hypothesis is that those rituals created group cohesion that held their society together. The social glue of monkey and ape societies is grooming, but humans seem to have , and those early rituals further cemented the bonds.

The culture’s killing implements abruptly appeared in the archeological record and disappeared just as fast, after the easily killable megafauna went extinct. Today’s North American megafauna are , not North American megafauna that learned to avoid humans. Bison are the only significant exception, although they came from Asia, too, and explaining their survival remains a minor curiosity, but is about the only circumstance not neatly aligned with the overkill scenario. The “” paper concluded that although the South American extinction was the greatest of all, it is the most poorly investigated and that the overkill hypothesis cannot yet be attached to South American extinctions. That may be a prudent position for a specialist who pronounces judgment only when all the evidence is in, but I will be among the most surprised people on Earth if the pattern of 50 thousand years did not continue there, especially since it had no ice sheets. There can be no more pertinent example than comparing Africa to South America. They inhabited the same latitudes and have similar climates, separated by the Atlantic Ocean. Africa was the home of humanity, where its animals had millions of years to adapt to the human presence, and Africa only lost about 10% of its megafauna (probably to human hunters with their advanced weaponry) while South America lost nearly all of its megafauna, and quickly. Climate change did it? How could it have even contributed?

Many traits of apes, including humans, are evident in monkeys. , which is when species have genders of different shapes and sizes, is a . But it is , especially apes, and is why men are larger and stronger than women. Its : how females choose their mates. A prominent hypothesis is that early monkey troupes had males as sentinels guarding the territorial perimeter and protecting the female-dominated core where offspring were cared for and where food was. A defensible food source was the key attribute of any simian territory. Most primates are , and extreme territorial behaviors can be seen in monkeys and apes, including murder, with its apotheosis in humans.

With the success of the end-Cretaceous bolide hypothesis, there was a movement in some circles to explain mass extinctions with bolide events, . If bolide events were responsible for all mass extinctions, then the , galactic explanation might still have relevance. Even though an end-Permian bolide event was unveiled with great fanfare and media attention in 2001, it does not appear to be a valid extinction hypothesis today, and invoking bolide impacts to explain mass extinction seems to have been a passing fad that has seen its best days. The oxygen hypothesis for explaining extinctions, evolutionary novelty, and radiations is similarly called a current fashion in some circles, and time will tell how the hypothesis fares, although it seems to have impressive explanatory value.

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Sauropods seem to have . Until relatively recently, animals as agents of ecosystem change and maintenance was a marginal idea. But today, is thought to be a seminal geophysical event in the Cambrian, and those huge sauropods probably had an ecosystem impact like what elephants have today in Africa. Elephants today break up woods as they feed, as they knock over trees and uproot them. That damage transforms the biome and provides opportunities for other kinds of herbivores and their predators. Elephants also and are considered , which have an outsized impact on their environment. Today, there is a “” to the overkill hypothesis regarding megafauna extinctions soon after humans appeared; such people minimize the impact of humans (their position has an inherent conflict of interest, as those ) and attribute the extinction of elephants of the Western Hemisphere (, ) to climate change and resulting changes in vegetation. If the current situation with African elephants is relevant, it is likelier that those vegetation changes were a of elephant extinction, not a cause. Elephant extinctions would have affected many other kinds of plants and animals, and could have precipitated . Similarly, those huge sauropods would not just have nibbled at vegetation and been relatively harmless browsers, but their vast bulk would have been ideal for pushing over trees to get at their foliage and other devastations of trees in particular, which would have dramatically impacted biomes. Giant dinosaurs probably had keystone species impacts on their environments, particularly the vegetation. Dinosaurs were not the only huge organisms in those days. The appeared in the Jurassic, and would have been immune to dinosaur browsing when they grew large enough. Below is an artist's conception of a typical Jurassic landscape (just as an allosaur and stegosaur are about to cordially interact). (Source: Wikimedia Commons)

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Just as the aftermath of the appearance of complex life was uninteresting from a , as the amazingly diverse energy-generation strategies of archaea and bacteria were almost totally abandoned in favor of aerobic respiration, biological solutions to the problems that complex life presented were greatest during the Cambrian Explosion, and everything transpiring since then has been relatively insignificant. Animals would never see that level of innovation again. While investigating those eonic changes, many scientists have realized that the dynamics of those times might have been quite different from today’s, as once again may be of limited use for explaining what happened. Also, scientists generally use a rule-of-thumb called , or parsimony, which states that with all else being equal, simpler theories are preferred. , a seminal theorist regarding the scientific method, as they were easier to falsify. However, this issue presents many problems, and in recent times, theories of or speciation have invoked numerous interacting dynamics. Einstein noted that the more elegant and impressive the math used to support a theory, the less likely the theory depicted reality. Occam’s Razor has also become an unfortunate dogma in various circles, particularly , in which the of materialism and establishment science are defended, and often quite irrationally. Simplicity and complexity have been seesawing over the course of scientific history as fundamental principles. The recent trend toward multidisciplinary syntheses has been generally making hypotheses more complex and difficult to test, although and ever-increasing and more precise data makes the task more feasible than ever, at least situations in which are not interfering.